code: def must_be_set(cls, v):
      if isinstance(v, str):
          return {v}
      if not isinstance(v, set):
          return set(v)
      return v
  
file_path: towhee/towhee/runtime/check_utils.py
imports: from typing import Dict, Any, Set, Tuple, Optional
  import re
  from pydantic import BaseModel, validator
  from towhee.runtime.constants import WindowConst, FilterConst, TimeWindowConst
label_desc: Use image node_id 1 for calling the SetForm obj's underlying member method code with example usage: obj.must_be_set(cls, v) and returns: v, unknown, set